Voltage phase generator with increased driving capacity

Details Voltage phase generator with increased driving capacity Voltage phase generator with increased driving capacity

1999-02-26

2001-03-06

Nelms, David (Department: 2818)

Static information storage and retrieval

Read/write circuit

Including level shift or pull-up circuit

C365S189080, C365S226000

Reexamination Certificate

active

06198672

ABSTRACT:

CROSS-REFERENCE RO RELATED APPLICATIONS
This application is based upon and claims priority from prior Italian Patent Application No. TO-98-A000167, filed Feb. 27, 1998, the entire disclosure of which is herein incorporated by reference.
Additionally, this application is related to the applications “LOW CONSUMPTION BOOSTED VOLTAGE DRIVING CIRCUIT” and “VOLTAGE BOOSTING CIRCUIT FOR GENERATING BOOSTED VOLTAGE PHASES”, which were filed on the same day as the present application and commonly assigned herewith to STMicroelectronics S.r.l. These related applications are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor memory devices, and more specifically to a voltage phase generator for driving booster circuits of a memory device.
2. Description of Related Art
Integrated circuits, and especially memory circuits, use booster circuits to raise the voltage over the supply voltage for applications such as the driving of memory arrays word lines. Such booster circuits operate by capacitively charging internal nodes with multiple voltage signals that have a determined time sequence. The voltage signals have the same amplitude but a different phase shift, so they are commonly defined as voltage phases. The voltage phases are generated by appropriate voltage phase generators. For such a purpose, a voltage phase generator typically generates four voltage phases: two phases with an amplitude equal to the supply voltage, and two phases with a greater amplitude that is obtained through a voltage boosting circuit or “bootstrap”. Usually, such a greater amplitude amounts to nearly twice the amplitude of the supply voltage. The voltage phases with a raised voltage are known as “boosted” voltage phases.
FIG. 1
a
shows a conventional voltage phase generator
4
. A temporary memory circuit or bi-stable latch LTH is controlled by control signals ST
1
and ST
2
to pace a normal voltage phase FX (i.e., a signal having the amplitude of the supply voltage VDD) and a negated normal voltage phase FN (i.e., in phase opposition to the normal voltage phase FX). The voltage boosting circuits or bootstraps BT produce a boosted voltage phase FBX (i.e., having a greater amplitude than the supply voltage VDD) and a negated boosted voltage phase FBN from the normal voltage phase FX and negated normal voltage phase FN.
The advancement of the normal voltage phase FX and negated normal voltage phase FN towards the voltage boosting circuits BT is paced by a clock signal CK and a negated clock signal CKN, which are the main clocks of the integrated circuit. The four voltage phases described above are shown in
FIGS. 2
a
and
2
b
. The voltage phase generator
4
drives a booster circuit
1
, which is shown in greater detail in
FIG. 1
b
. The booster circuit
1
has two stages S
1
and S
2
that receive a supply voltage signal at an input IN and supply a boosted voltage signal from an output OUT. The booster circuit
1
may contain several stages that subsequently raise the voltage up to the desired value. The booster circuit
1
is substantially driven by the four voltage phases FX, FN, FBX, and FBN generated by the voltage phase generator
4
of
FIG. 1
a.
Both of the normal voltage phases FX and FN are generally subject to high current demands during charge transfers from one stage to the next in the booster circuit
1
. In contrast, the boosted voltage phases are primarily used to avoid threshold effects of transfer transistors M
1
and M
2
, which are responsible for charge transfer from one stage to the next. Conventionally, high currents are achieved by interposing driving stages
5
having high driving capacity on the normal voltage phases FX and FN that exit the voltage phase generator
4
. In other words, the circuit has driving stages
5
capable of supplying high current and formed by adequately-sized inverter circuits (i.e., with a high channel width to length or aspect ratio) that are capable of supplying the high current.
However, such aspect ratios tend to increase the peak current consumed by the inverter circuit during switching. Besides increasing consumption of the inverter circuit, this can also generate unwanted supply noise. Therefore, there is a drawback to using such inverter circuits in the inability to independently increase the aspect ratio of the transistors of the inverters to comply with any driving capacity requirements because the current consumed during switching also increases.
SUMMARY OF THE INVENTION
In view of these drawbacks, it is an object of the present invention to overcome the above-mentioned drawbacks and to provide a voltage phase generator that has a more efficient and improved performance.
Another object of the present invention is to provide a voltage phase generator that can supply normal voltages with a high driving capacity without using a large-sized inverter circuit.
One embodiment of the present invention provides a voltage phase generator that generates a normal voltage phase, a negated normal voltage phase, a boosted voltage phase, and a negated boosted voltage phase. The voltage phase generator includes a first driver circuit that supplies the normal voltage phase to a first output node, and a second driver circuit that supplies the negated normal voltage phase to a second output node. The first and second driver circuits are driven by additional voltage phases that have a boosted voltage. In one preferred embodiment, each of the driver circuits includes a pull-up connected between a supply voltage and one of the output nodes, and a pull-down connected between ground and the one output node.
Another embodiment of the present invention provides a voltage boosting circuit that includes a booster circuit and a voltage phase generator. The booster circuit receives four voltage phases and generates a boosted voltage, and the voltage phase generator generates the four voltage phases and additional voltage phases that have a boosted voltage. The additional voltage phases drive driver circuits that supply the normal voltage phase and the negated normal voltage phase to the booster circuit. In a preferred embodiment, the voltage boosting circuit is integrated in a low supply voltage circuit device.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention.


REFERENCES:
patent: 5097226 (1992-03-01), Pascucci et al.
patent: 5278786 (1994-01-01), Kawauchi et al.
patent: 5315167 (1994-05-01), Chan et al.
patent: 5334948 (1994-08-01), Fong et al.
patent: 5726944 (1998-03-01), Pelley, III et al.
patent: 5821639 (1998-10-01), Tailliet

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